Effects of Total Dissolved Gas Supersaturation on the Survival of Juvenile Procypris rabaudi and Juvenile Myxocyprinus asiaticus at Varying Water Depth in a Natural River.

Xiaoqing Liu,Chenyang Cao,Zhiqin Li,Yao Yang,Yuanming Wang,Haoran Shi,Wen Su,Liangfang Xu

doi:10.3390/ani11113061

Xiaoqing Liu, Chenyang Cao + Show 6 more

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https://doi.org/10.3390/ani11113061

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Abstract

Total dissolved gas (TDG) supersaturation, which can be caused by flood discharge, results in gas bubble disease (GBD) in fish and threatens their survival downstream of dams. TDG supersaturation has become a serious environmental problem in the Yangtze River. Few studies have evaluated the effect of TDG supersaturation on fish in natural rivers during periods of flood discharge. To estimate fish tolerance to TDG supersaturation under natural conditions, juvenile Myxocyprinus asiaticus and juvenile Procypris rabaudi were exposed to TDG-supersaturated water for 96 h at various depths (0-0.3 m, 0.3-1.3 m, 1.3-2.3 m and 0-2.3 m) during periods of flood discharge of Dagangshan hydropower station. The results showed that juvenile Procypris rabaudi and juvenile Myxocyprinus asiaticus exhibited obvious GBD signs. An increase in exposure time decreased survival probability of the two species. Deeper water depths can increase the tolerance of juvenile Procypris rabaudi to TDG supersaturation in natural rivers during periods of flood discharge while it cannot improve the survival of juvenile Myxocyprinus asiaticus. Compared with juvenile Myxocyprinus asiaticus, juvenile Procypris rabaudi showed weaker tolerance of TDG supersaturation in shallow water, and juvenile Procypris rabaudi were more vulnerable to TDG supersaturation than juvenile Myxocyprinus asiaticus even if the TDG level (116%) was low.

Highlights

IntroductionDissolved gas supersaturation is a condition that results from natural processes (e.g., water cascades, changes in water temperature, photosynthesis) and human activity (flood discharge) [1,2,3,4,5]
Dissolved gas supersaturation is a condition that results from natural processes and human activity [1,2,3,4,5]
Our study indicates that deeper water depths can increase the tolerance of juvenile Procypris rabaudi to total dissolved gas (TDG) supersaturation in natural rivers during periods of flood discharge while it cannot improve the survival of juvenile Myxocyprinus asiaticus

Summary

Introduction

Dissolved gas supersaturation is a condition that results from natural processes (e.g., water cascades, changes in water temperature, photosynthesis) and human activity (flood discharge) [1,2,3,4,5]. The signs of GBD and its mortality rate in fish, such as Esox lucius, Pomoxis nigromaculatus and Oncorhynchus tshawytscha, have been reported due to dissolved gas supersaturation [9,10,11]. When floodwaters are released from these high dams, total dissolved gas (TDG) supersaturation occurs in the water downstream of the dams. TDG supersaturation maintains a high saturation level (130–143%) downstream of Three Gorges Dam and Ertan Dam during periods of flood discharge [5,12]. This may cause fatal effects in fish due to GBD. In 2014, the flood discharge at Xiluodu Hydropower Station caused the death of 40 tons of fish

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